1. Field of Invention
The present invention relates to wells drilled in water-covered areas. It relates especially to a device for releasing a releasable connection between a casing cemented in a hole drilled in the water bottom and a riser pipe which extends from the casing to the water surface.
2. Setting of the Invention
In recent years, there have been a large number of oil and gas wells drilled in water-covered areas. The depth of the water may range from a few feet to a thousand or more. In these cases, the well is drilled in the ocean floor and a casing, which is a steel pipe of large diameter, is set and cemented in the wellbore. Sometimes the wells are completed on the bottom of the ocean floor. By completed, it is meant that the wellhead, or the top, is capped at the ocean floor and arranged with various conduits and valves so that fluid may be produced from the well in a controlled manner. In many cases, however, it is desired to connect a riser pipe (e.g., a large diameter steel pipe) to the well casing in a sealing engagement thereto so, in effect, it extends the well casing to a floating vessel above the water surface.
3. Prior Art
There are many couplings or connectors available for connecting a riser pipe to a subsea wellhead. Perhaps the closest prior art is U.S. Pat. No. 4,138,148, issued Feb. 6, 1979, entitled "Split Ring Riser Latch" issued to Hubart B. Zaremba, assignee, Standard Oil Company (Indiana). The releasing tool disclosed herein is structurally different and operates on a different principle than that of the prior art.